With continuous development of communication technologies, for purpose of improving the performance of data transmission, a data sending end (for example, a node B (NodeB), a base station (BS), or the like) may be configured to obtain a PM according to a Precoding Matrix Indicator (PMI) fed back by a data receiving end (for example, a user equipment (UE), a mobile station (MS), or the like) and a codebook pre-stored locally so that data to be sent are pre-processed through the PM and then sent to the data receiving end. In this way, a data sending process can be adaptive to variations in channel statuses so as to improve the performance of data transmission. Therefore, how to acquire a PMI and which kind of codebook is to be used are of vital importance.
The existing Long Term Evolution Release 8 (LTE R8) system supports 4-antenna transmission and employs a single fixed codebook which is obtained based on Householder reflection. In the existing Institute of Electrical and Electronics Engineers (IEEE) 802.16m system, a non-differential codebook and a differential codebook are employed, and feedback is performed mainly in a differential mode in the following process: in each preset feedback period, the UE firstly feeds back one non-differential PMI based on the non-differential codebook and then, according to the non-differential PMI, feeds back a plurality of differential PMIs based on the differential codebook in sequence.
During implementation of the present invention, the inventor finds that at least the following problems exist in the prior art:
In the existing LTE R8 system, a single fixed codebook is employed, the sub-band feedback suffers from a high overhead, and the broadband feedback has a low precision. In the existing IEEE 802.16m system, the time-domain differential feedback is employed, and acquisition of a PM relies on historical information of the feedback, which may cause the problem of error propagation. Moreover, because of characteristics of elements in each of codewords included in the differential codebook used in the existing IEEE 802.16m system, the PM finally obtained may not have a constant modulus characteristic, and particularly, it is difficult to satisfy the finite character set (for example, 8 phase shift keying (8PSK)) constraint characteristic of each of the elements. Furthermore, it has been found through an experiment that when, in the aforesaid differential feedback, the codebook in the LTE R8 system is directly used as the non-differential codebook and the differential codebook of the IEEE 802.16m system is employed, the overhead is high and the feedback performance is scarcely improved compared to that when only the LTE R8 codebook is used for feedback, resulting in a low efficiency per feedback bit. Therefore, it is necessary to make further research on the structure of the feedback and the codebook used for the feedback in order to improve the feedback performance of the system.